Vibrating method to enhance oil recovery

ABSTRACT

A vibration impact method on to enhance oil and gas recovery from productive geological formations by controlling phase surfaces of seismic waves to focus elastic energy on localized areas.

BACKGROUND OF THE INVENTION

The present invention is in the technical field of oil and gasproduction. More particularly, the present invention is provided amethod of enhanced oil recovery through the vibration impact on the oilcontained formation.

Oil and gas companies consistently look for advanced technologies toincrease recovery and intensify fluid inflow from wells in thehydrocarbon production process—particularly with deposits in complexreservoir conditions such as compacted oil reservoir rocks, high watercuts, and irregularly distributed permeability zones created byhydraulic fracturing. The interest of companies is essentiallyindependent of the oil market since recovery and intensificationtechnologies increase production volumes without significantly raisingcosts, as oilfield infrastructures need not be otherwise modernized orimproved.

One of the methods of oil recovery enhancement is the use ofseismic-acoustic reservoir stimulation methods [1-6]. Elastic(vibrational) influence on productive formations has emerged as apromising solution with the demonstrated influence of wave processes onfluid kinetics in multicomponent (oil, gas, water) and multiphase (gas,gas condensate, gas hydrate) flows.

Among these enhanced oil recovery technologies are those based on thevibrations excitation from the earth surface. The effect of seismicelastic waves on oil recovery was discovered in 1985 by the Institute ofEarth Physics, USSR Academy of Sciences on the Abuzy oil field locatedin the Krasnodar region [2] of Russia. The method was carried out usinga 20-ton vibrator on the earth's surface in the frequency range of 10 to30 Hz. The energy of density flux in the oil reservoir did not exceed10⁻³-10⁻⁴W/m2. As a result, an increase in oil production of 5-10% wasachieved by decreasing the water cut from 90-95% to 85-90% in producingwells. Repeated experiments showed that this effect persisted for atleast one month. Following these results, the theoretical,methodological and technological aspects of the specified researchdirection were intensively developed [7-13].

For the last several decades, new principles and devices for vibratorystimulation [14-17] of oil and gas reservoirs have been developed, whileextensive theoretical studies [18-26], as well as modeling and fieldexperiments, have also been conducted.

Currently, the interest in vibratory stimulation of oil reservoirs isgrowing again. Uses of ultrasonic equipment and technology for oilfieldstimulation in Russia and in the United States [27-30] have confirmedthat acoustic impact can improve the oil recovery ratio. This issue isthe subject of international discussions [31].

Since the mid-20th century, numerous methods and devices have beendeveloped for elastic impact on geological objects containing oil andgas in order to increase the hydrocarbon recovery rate, including:

-   -   global reallocation of the mechanical properties of the rock        massif through a powerful explosion or hydraulic impact [32-36];    -   excitation of acoustic oscillations in the borehole and/or in        the wells group [37-53];    -   ultrasonic and electromagnetic waves emission, including        selective action on a porous environment (rock) and on the        fluids within the pores (oil, gas, water) [54-63];    -   low-frequency impact through sequences of depressions and        repressions on a zone saturated with hydrocarbons [64-73].

Yet solutions of vibrational impact from the Earth surface have not beendeveloped to address the oil and gas services market's need, as withoutexpensive, special equipment and other costs, explorers have been unableto create the density of elastic energy needed to use this method withinthe defined yet extensive areas of the hydrocarbon reservoir. Despitenumerous theoretical and experimental studies, a constructive solutionto this problem has not yet been found.

At the same time, techniques of adjustable wave front focusing have beenapplied and developed throughout the entire existence of seismic mineralresource prospecting. This is for the most part in reference toso-called “laboratory” variants, in which wave focusing is synthesizedfor processing recorded data. There are also various solutions forphysically realizing group directed (focused) sources of seismic waves,for example [74-75]. But these solutions are aimed at increasing thesignal-to-interference ratio in the process of recording and processingdata.

Thus, the present invention proposes a solution to the problem ofintensifying oil and gas production using the methodology and equipmentdemonstrated in another (geophysical) industry where they are using toimprove the accuracy and reliability of seismic research results.

SUMMARY OF THE INVENTION

The present invention is a new method of enhancing oil recovery throughseismic vibration, in which oscillations are excited on the surface ofthe earth. The proposed solutions differ from existing ones because theyprovide control to phase surfaces of seismic waves in order to focuselastic energy in the localized area of an oil or gas reservoir.

Using a large number of seismic vibrators with controllable delay willenable accumulation of signals energy in-phase. As a result, the highdensity of elastic energy will be concentrated in a local area.

Wherein, the surface vibration in the area of the production facilitieswill not damage the infrastructure, because the process is similar toseismic studies with vibrators that are common in oil and gas fieldregions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1. Simplified scheme of a focused elastic exposure on a geologicalformation.

FIG. 2. General initial conditions of a model of an oilfield elasticstimulation system.

FIG. 3. Main regularities of the energy flux density distribution (aprocess of elastic energy focusing in a digital model).

FIG. 4. Energy flux density dependence by the number of vibrationsources (a digital model of the elastic energy focusing process).

FIG. 5. Controlling the position of the area of focus in the lowerhalf-space (a digital model of the elastic energy focusing process).

FIG. 6. Generalized dependence of the energy flux density on theposition and depth of focus and the number of vibration sources (adigital model of the elastic energy focusing process).

FIG. 7. An interaction of the main components of the elastic stimulationsystem in an oilfield.

FIG. 8. Technology flowchart of the implementation of the vibratingmethod for enhancing oil recovery.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the invention in more detail, FIG. 1 shows thesimplified scheme of a focused elastic impact on the geologicalformation. The numbers shown in parentheses refer to location points onthe attached Figures.

Numerous seismic sources (node 10) are placed on the surface. The numberof the sources (10) and their relative positions on the surface arechosen based upon the technical requirements of depth location andenergy distribution within the area of focus for elastic stimulation.For clarity, FIG. 1 shows action for only three sources (10). Inpractice, 10, 15 or more of the sources (10) are used. The start time ofeach source (10) is set so that the fronts of elastic waves or the linesof equal propagation times of the waves (11) are crossed in the centerof the elastic energy focus area. For homogeneous velocity models, thetime of elastic wave propagation between the focusing point x _(f) andthe oscillation source position x _(i) is

${t\left( {{\overset{\_}{x}}_{f},{\overset{\_}{x}}_{i}} \right)} = {\frac{\sqrt{\langle\left. \left( {{\overset{\_}{x}}_{f} - {\overset{\_}{x}}_{i}} \right) \middle| \left( {{\overset{\_}{x}}_{f} - {\overset{\_}{x}}_{i}} \right) \right.\rangle}}{V} = {T_{i}.}}$

where <|>—denotes the operation of the vectors' scalar multiplication.

If the oscillations are generated by the sources (10) at each point x_(i) with a time delay in accordance with equation

ΔT _(i)=(T _(o)-T _(i)),

the corresponding spherical waves fronts (11) at time T_(o) (of V*T_(i)radius) are intersecting at the x _(f) point.

All other fronts positions, located before and after T_(o), will notintersect but will concentrate in regions (12) and (13). So, thedimensions of the area will be determined by the difference between theisochrones value and T_(o).

Thus, an in-phase interaction of waves from different sources (focusing)will occur only in the proximity of x _(f). At other points, to agreater or lesser extent, the accumulable signal will be weaker due tothe antiphase interference effect. The power-stream will changeaccording to the signal amplitudes as it shows by (14). Therefore thedensity of elastic energy will reach the maximum value in the focusingzone near x _(f).

There are three types of elastic wave sources in the practice of seismicexploration of mineral deposits: 1) explosive (explosives placed inspecial wells); 2) non-explosive pulsed (mechanical, pneumatic,electro-dynamic impact or explosion in an isolated space); and 3)vibrational (a vibrational platform on a heavy truck chassis). There areno significant restrictions on the use of the above-mentioned sources ofelastic waves to stimulate the reservoir, but some important factorsshould be considered. Different source types have different energycharacteristics, as well as different risks of environmental damage.Presently the most common method for excitation of elastic waves is thevibration method. Apart from the degree of environmental safety theyafford, such sources have wide control ranges in frequency and durationof elastic impacts as well as advanced automatic controls for equipmentoperation.

In order to demonstrate the feasibility of the invention underconsideration, and the possibility of achieving the main objective,regulated energy levels and the duration of the elastic effect are usedin a digital model of the propagation of elastic oscillations in aninfinite continuous medium. This type of simulation is an alternativeapproach to a difficult, costly field test.

FIG. 2 shows the initial conditions of modeling. The position of theoscillation sources on the day surface (21) is assumed to be symmetricwith respect to the central point of the coordinates system and isdetermined by the number of such sources Nx, Ny and the steps dX, dY oftheir placement along the X and Y axes, respectively. For a givenvelocity of elastic waves propagation V and the focusing point in thelower half-space x _(f) the distribution of elastic energy density inthe bounded region—the “cube” (22)—is calculated given the position ofthe center at point x _(o) and by dimensions along the correspondingcoordinate axes. The sweep-signal (23) is determined by the values ofthe maximum and minimum boundary frequencies f_(max), f_(min) at thetime interval 0-t_(max), at a which the maximum amplitude=1. The powerflux density is calculated in Joules per second (watts) per unit area(square meters)−[J/(m²*s)].

The main factors that affect the distribution of energy of elastic wavespropagating in a continuous medium are geometric divergence and powerabsorption. The first factor expresses the law of the energyconservation. In the given case, the consequence of such a law is adecrease in energy density in proportion to the increase in the area ofthe wave front surface which has been moved continuously away from thesource. The second factor is determined by the properties of the rockmassif as a porous environment saturated with liquid or gas.

The elastic medium could be described for the ray-approximation in thegeneralized form as

${{\sum\limits_{n = 0}^{2N}{\vartheta_{n}{\frac{\partial^{n + 2}}{\partial t^{n + 2}}\left\lbrack {U\left( {\overset{\_}{x},t} \right)} \right\rbrack}}} = {\sum\limits_{n = 0}^{2N}{\mu_{n}\Delta \left\{ {\frac{\partial^{n}}{\partial t^{n}}\left\lbrack {U\left( {\overset{\_}{x},t} \right)} \right\rbrack} \right\}}}},$

where U(.)—the amplitude of elastic wave; Δ is the Laplace operator;ϑ_(n)=ρν_(n); ρ—the density; ν_(n),μ_(n)—rheological modules of themedium that slowly change in spatial coordinates and do not depend ontime .

This form of the equation describes all dissipation mechanisms ofelastic energy, including ones most used in similar considerations:

-   -   Hooke's body, characterized by the fact that there are only        purely elastic stresses in the environment;    -   Kelvin-Voigt body, in which along with elastic forces there are        additional stresses due to viscosity, proportional to the        velocity of deformation;    -   Maxwell's body, in which the tensions arise during deformation        and gradually relax, such that when the load is lifted, the body        does not return to the previous state; there are always residual        deformations;    -   Standard linear body, which takes into account both of these        absorption mechanisms.

To solve the problem of estimating the distribution of elastic energy ina medium, the account of the wave dissipation (partially inelasticscattering) effect can be reduced to describing the wave eikonal as afrequency dependent on

${{\tau \left( {\overset{\_}{x},\omega} \right)} = {\int\limits_{0}^{M{(\overset{\_}{x})}}\frac{dS}{V_{e}\left( {\overset{\_}{x},\omega} \right)}}},{{{with}\mspace{14mu} \frac{\partial\tau}{\partial\xi}} = {\frac{\partial\tau}{\partial S} \cdot \frac{\partial S}{\partial\xi}}},{{{and}\left( {\nabla\tau} \right)}^{2} = {{\frac{1}{V_{e}^{2}}\left\lbrack {\left( \frac{\partial S}{\partial x} \right)^{2} + \left( \frac{\partial S}{\partial y} \right)^{2} + \left( \frac{\partial S}{\partial z} \right)^{2}} \right\rbrack} = \frac{1}{V_{ee}^{2}}}}$

The delay function of the signal's components in the medium τ(x,ω), issimilar to a time function. It is smooth, it can be differentiated anddetermined through effective parameters—such as effective velocity orthe timing of the arrival of waves—used in the kinematic problems of theseismic survey.

Nevertheless, in this case there is a ray-transformation in accordancewith which both geometric and absorption factors can be taken intoaccount.

The problem consists of constructing signal parameter distributions(energy density and spectral characteristics) for various combinationsof medium properties, source placement, and signal focusing zonelocation per coordinates.

It is worth noting the theoretically described and experimentallyconfirmed priority of surface waves in the energy balance of the elastic(vibrational) impact on the ground-air interface. Most of the energy ofthe source (65-70%) is expended on the formation of surface waves, andonly 30-35%—on that of volumetric waves. In addition, it is essential totake into account the properties of the near-surface (loose) zone aswell as the influence of the contact between ground and vibrator.

Virtually all real geological environments are much more complicatedthan every velocity model considered above. However, modern seismicsurveys systems have all the necessary means for correctly predictingthe conditions for focusing the wave field in any complex conditions. Tosubstantiate the technical possibility and advisability of focusingelastic energy in a geological environment, it is sufficient toapproximate the main factors that influence this process. Withray-transformation both geometric and dissipation factors can be takeninto account. So the problem consists of constructing signal parameterdistributions—energy density and spectral characteristics, for variouscombinations of medium properties, source placement, and signal focusingzone location.

In the first modeling phase, we confine ourselves to a narrow, 10-30Hertz seismic signal range. Such oscillations are weakly absorbed by thereal medium and contain the main share of volumetric seismic wave energy(if they are emitted from the surface). In addition, serial seismicvibrators are the most stable and reliable in this frequency range,producing power of up to 300 kilowatts.

FIG. 3 shows how the primary regularities of elastic energy focusingchange in the model conditions described above. Parameter values areshown in the table as the numbers for each option. Model energydistributions are formed for a horizontal cross-section of the focusingdomain. The result is normalized, since in this case the shape of thesignal and its relative change in the focus area—rather than theabsolute value—is important.

In accordance with general theoretical assumptions, an increase in thesweep frequency from 10-30 Hz (option 31) to 30-60 Hz (option 32)narrows the coherent imposition area of the signals from differentoscillation sources. Accordingly, the focusing area along the X and Yaxes is reduced in proportion to the increase in the original signal'sfrequency. At the same time, in the harmonic mode at 50-50 Hz (33)so-called “mirror” effects appear, associated with a quasi-coherentaccumulation of oscillations in the point positions, where the distancesto the sources is a multiple of the emitted wavelength.

Options (34-35) illustrate a “quality factor”: the nonlinear dependenceof the signal focusing system on the distance between surfaceoscillation sources. When the sources are placed at distancescommensurate with the wavelengths, in this case −0.2 km (34), the signalfocusing area expands. If the removal of oscillation sources arecommensurate with the focusing depth −1 km (35), it is much moreeffective with regard to in-phase signal accumulation and focus zonelocalization. At the same time, a further increase in deletions of up to1.5 km does not significantly manifest in the model.

All things being equal, the energy flux density is determined by thenumber of elastic vibration sources in the group. In FIG. 4, thisdependence is shown using the example of one source (option 41), ninesources (42) which are located symmetrically with respect to the centerof the group [3×3], and twenty-one sources (43) which have grouped as[7×3]. The distribution of elastic energy flux density in the vicinityof the focusing point is shown in the horizontal section by the XOYplane and in the vertical section by the XOZ plane. In the case of asingle vibrator (there is no focusing), the indicated energy parametersmoothly decreases along coordinates in accordance with geometricdivergence and dissipation rules. The magnitude remains in area 10⁻² [J/(m²*s)]. With an increase in the number of oscillation sources to 9(42), a region of increased power density (44) appears, up to 1.0 [J/(m²*s)] at 9 sources and up to 4.0 [J/ (m² *s)] at 21 sources,respectively. In accordance with elementary theory, the energy in theharmonic oscillator model should be in a quadratic dependence on theamplitude. So the amplification of the signal in with 9 oscillatorsources should lead to increase in energy of 81×. However, since thegeometric divergence and dissipation processes are operating constantly,this value (at a given focusing depth, frequency range, and wavevelocity) decreases to about 50. Similarly, 21 vibration sources wouldyield a value not of 441, but 200. The reduction is significant, but notfundamental.

The symmetry breaking in the location of the source on the surface hasbeen inherited in the structure of the signal focusing area. In the caseof (43), the number of vibrators along the Y-axis is smaller than alongthe X-axis. Therefore, this area expands along Y. However, the intensityof the side maxima (45) decreases with an increase in the number ofsources.

An important practical problem of elastic energy focusing technologyimplementation for enhancing oil recovery is the possibility of changingthe focusing region position in the lower half-space without movingoscillation sources on the earth surface.

FIG. 5 shows the model representations for the three focus positions: 0km, 0.5 km and 1.0 km in coordinate X and its three positions: 2.5 km,3.0 km and 3.5 km in coordinate Z, with a fixed placement of 21vibration sources on the surface. The initial modeling parameters andthe results are related to each other by option numbers (51-59). Withdepth, the energy efficiency of focusing naturally decreases; thehorizontal displacement increasingly affects the shape of the focus areaof the signal and, to a lesser extent, its intensity. It should be notedthat the intensity changing at the region of +/−1 km horizontally and 1km vertically (with a fixed position of the source group), remainswithin 30% -35%, relative to the “average position” x _(.)=(0,0,3).

The most important feature of the invention, however, is the limitednumber of vibrators −N, that can be used in a group composition for thesignal focusing. Large seismic survey projects suggest the simultaneoususe of dozens of elastic wave sources. At the same time, existing sourcemanagement tools in the group provide a wide range of control overoperating modes such as start time, duration of operation and sweepsignal parameters.

FIG. 6 presents the results of modeling the dependence of energy densityon the N and signal focusing depth. This is the actual change in energydensity [J/(m̂2*s)] when N increases from 0 to 40 for a constant depth offocus (61) and energy density increment [J/(m²*s)] when N increases perunit (62). The focusing depth [km] for each curve is shown the callouts.Due to the influence of the above-mentioned processes of geometricdivergence and dissipation, the greatest energy in the focusing effecttakes place at shallow depths of 1-2 km. With increases in depth, thisexpression of energy is leveled, while absolute values of energy densitycorrespondingly decrease. For a depth of more than 5 km, with the N=40,the density of elastic energy no longer reaches 1 [J/(m²*s)].Nevertheless, for N=20-30 units, this value is two orders of magnitudehigher in comparison with the case N=1.

In sum, the main conclusions of the results of simulation are:

-   -   Focusing of seismic signals from a plurality of vibration        sources provides a concentration of elastic energy in a limited        volume of the lower half-space, commensurate to the wavelength        of the lower frequency sweep signal;    -   The location of the focusing area in the medium can be        substantially changed through surface and depth coordinates        without changing the vibrator system position, as well as        without significant losses of energy efficiency;    -   An increase in the power flow in the focus area of the signal        and the density of elastic energy from a number of sources in        the group (N=10-30) is achieved approximately N^(1,3)-N²        compared to a single vibrator use.

All the above arguments confirm the possibility of constructing anindustrial technology for elastic impact on hydrocarbon reservoirs fromthe day surface to enhance oil recovery, using existing field equipmentand seismic survey information systems.

FIG. 7 displays an interaction of the elastic stimulation systemcomponents in the reservoir. The sources of seismic waves (71) have beenpositioned on the day surface with the proper relative distance anddistribution. In addition, the conditions are observed for safe removalof the powerful vibrating installations in the surrounding productionfacilities and constructions.

It is possible to use both variants of source positioning accepted inseismic prospecting with given coordinates (topographical pickets) aswell as arbitrary landmarks, with subsequent measurement of coordinatesby GPS. The sequence of switching on the vibrators is set by the systemcontrol station in accordance with the current position of the signalfocusing point and the velocity distribution into the rock massif. Thestart time to actuate each source (71) is calculated so that the initialphases of elastic vibrations from all sources coincide in apredetermined focus point. At some point in time, the wave fronts (73)occupy the position shown in the figure. In the vicinity of the point(74), the fronts of elastic waves (lines of equal propagation times)from different sources intersect with each other. As a result, elasticwaves from each source are added together in equal phases. The processcan be repeated cyclically:

-   -   For accumulation of elastic energy at a given focus point;    -   To extend the impact zone within the reservoir, the focus point        has been shifted but the location of the sources remains        unchanged;    -   For moving to another object (seam) with a change in the        relative location of the vibrators, as well as the depth, shape,        and duration of the sweep signal.

A practical and significant adaptation of the present invention is anindustrial technology for increasing enhanced oil recovery (EOR) byelastic action from a daytime surface.

Traditionally, options in the implementation of such technologies havebeen described in oilfield recovery projects, where for each localdeposit (impact object) a particular program is defined that determinesthe modes and the execution of a sequence of the correspondingtechnological operations and events. FIG. 8 shows a technological schemeas a block diagram of the relevant basic procedures and cycles:

-   -   Procedure (81) provides for the systematization and storage, in        the form of a project database, of all information necessary for        project implementation in accordance with the spatial location        of impact objects—including:        -   Coordinates of the source positions;        -   The model of velocity distribution in the geological            environment and data for calculating the time delays in the            vibrator operation process;        -   Parameters of the sweep-signal for a given sequence of            signal focus points. All formats for the information digital            descriptions, as well as the data transferring protocols,            are determined by the technical regulations that are used to            carry out the project.    -   Procedure (82) presupposes placing sources of elastic vibrations        (71, FIG. 6) on the day surface, based on the project database        section content which applies to a current local hydrocarbon        object—including coordinates, size, and depth of the reservoir        location.    -   Procedure (83) provides an initial setting of operation control        parameters for the previously positioned sources of elastic        vibrations. The specified program is executed through the        station (72, FIG. 7) to set the given position and modes of the        signal focusing process.    -   Procedure (84) generates a set of commands and control        parameters for triggering a single impact in a given zone of a        local hydrocarbon deposit. As part of the control function,        sweep-signal parameters have been established in accordance with        predicted characteristics of energy distribution in the focus        area (74, FIG. 7) as well as the table of the start time for        each elastic vibrations source (71, FIG. 7). Before the        procedure ends, the control station (72, FIG. 7) checks the        system to ensure it is ready to work and then sends the command        to start it.    -   Procedure (85) is performed automatically by all elements of the        system in accordance with the program of elastic impact through        the station (72, FIG. 7).    -   Cycle (86) presupposes repetition of processing a given focus        area to achieve the given elastic impact duration in accordance        with the project.    -   Cycle (87) involves the moving the energy focusing area within        the local target object.    -   Cycle (88) involves reinstallation of the focusing system to a        new layer or another productive formation located above or below        the current impact object.

There is significant potential in employing wave processes generated onthe earth surface for oil and gas fields recovery. In this case, thereis a possibility of volumetric concentration of elastic energycommensurate with the energy intensity of formation flooding underexternal pressure and other advanced oil recovery technologies.According to some experts, this is essential not only for both therecovery of depleted (marginal) deposits and the stratum-fluid conditionoptimization of objects in the initial field development phase.

Among the issues associated with the use of such elastic energy, threedeserve special attention:

-   -   1. The possibility of controlling the energy level in the        localized area of a geological environment.    -   2. The conformity of vibration energy with respect to mechanical        properties of a reservoir system.    -   3. Modern seismic vibration technologies do not harm oil or gas        production infrastructures.

There are also significant prospects for the application of more complexschemes of elastic impact on formations both in combination with knownseismo-acoustic (primarily borehole ultrasonic) and geomechanical(primarily depressive-repressive and hydro-shock) technologies.

Data from geophysical research has made it possible to construct a wavefield model in a real environment with high precision. This modeldefines the kinematic characteristics of focused elastic waves emittedfrom the surface.

The usage of elastic wave focusing enables control of the signal levelin the environment. Substantial changes in the relative energy ofelastic impact near the focus point (in the wavelength range of about30-80 meters) affect the physical characteristics of the fluid-filledpore space, but do not destroy the well's casing or the cement sheatharound the casing.

All this creates favorable prerequisites for the production practicalapplication of the present invention.

The usage of the elastic waves focusing provides the possibility tocontrol the signal level in the environment. Substantial changes in therelative energy of the elastic impact near the focus point andinsignificant distance from it (in the wavelength range of about 30-80meters), affect the physical characteristics of the pore space filledwith fluid but does not destroy the well's casing or the cement sheatharound the casing.

All this creates favorable prerequisites for the production practicalapplication of the present invention.

What is claimed is:
 1. A method of enhanced oil recovery through elasticimpact on productive formations based on the use of vibration sourcesand control units utilizing seismic surveys. The method is characterizedby the concentration of elastic energy on local areas in the rockmassif, with the dynamic, duration and intensity of the impactsregulated according to the distribution, shape, size, and location ofthe effect zone. The method utilizes numerous elastic wave sourceslocated at varying distances from each other. In accordance with thesedistances and the distribution of the massif's elastic parameters of themassif, the start time, duration and parameters of the emitted signalsare tuned for each oscillation source to focus waves in a given zone ofimpact. The energy efficiency necessary for enhanced oil recovery isachieved through cyclical repetition of focused elastic impact action.Damage to environment and to the production infrastructure are alsominimal compared to other methods.
 2. A method according to claim 1: Tooptimize the elastic impact on the porous collector and thehydrocarbon-fluid in the pore space, several groups of oscillationsources are used—each of which is tuned so that the wave can be focusedwith the different dynamic characteristics needed to influence the rockand fluid, respectively. As the elastic waves from vibrational sourcesare being focused, their spectral composition and the duration ofelastic oscillations stream (sweep-signal parameters) can also bealtered.
 3. A method according to claims 1-2: In order to improve theefficiency of oil recovery enhancement, the focusing of elastic energyis consensual in time with other processes of the fluid inflowintensification, such as a depression and repression sequences,ultrasonic, electromagnetic and magnetostrictive stimulation methods inthe wells. The dynamics of the elastic action—and, accordingly, theoperating modes of the vibration sources (groups of sources)—areconsistent with the dynamics of these processes.